Enhance Your Cellular Power
All modern cells are likely to be descendants of a single ancestor species that carried a
‘‘proto-mitochondrion,’’ an ancestral original mother, the “Eve” at the creation of modern cells.
By Will Block

A living cell requires energy not only for all its functions,
but also for the maintenance of its structure. —Albert Szent-Gyorgyi

bout 2 billion years ago, eukaryotes (pronounced eu·cary·otes)—the first organisms whose cells contain nuclei with its DNA arranged in chromosomes—found it useful to host bacterial invaders within their membranes. Think of eukaryotes as martial artists, who cunningly diverted the energy of bacteria and induced them to take up residence within their cells. There, for the value of protection from outer worldly chaos, the bacteria paid rent, using the currency of their evolutionary knowledge. And as with any fair social exchange, the eukaryote hosts offered some of their know-how to the enveloped bacteria.* Thus began a symbiosis of these organelles with their eukaryote hosts. The organelles are mitochondria, and we humans are eukaryotes.

*Unlike cells of animals and other eukaryotes, bacterial cells do not contain a nucleus and rarely harbor membrane-bound organelles.

Mitochondria, the relics of an ancient species, are ubiquitous, double-membrane bound organelles, which have developed from precursor proteobacteria that have become endosymbiotic over the course of evolution.1 As energy workhorses, mitochondria are equipped with outer and inner membranes possessing sets of membrane proteins required for energy conversion, membrane fusion and fission, metabolite and protein transport, and signal transduction.

Encoded by Two Genomes

The membrane proteins of the mitochondria are encoded by two genomes, that of the cell’s nucleus and that of the mitochondria, which display divergent effects on the two membranes with regard to their topologies.

For cellular integrity, proteins must be correctly targeted and assembled into functional protein complexes. They must also be tightly regulated and mediated by the coordinated functions of import/export machineries resident on both the outer and inner membranes of the mitochondria.

The “Eve” of the Modern Cell

While the machinery of the mitochondria that moves proteins into or out of the organelle is thought to have been commandeered by the eukaryotes, the enzymes that help import protein into mitochondria have no apparent counterparts in bacteria.2 Thus it is likely that these mechanisms of movement were created from the beginning (de novo) of the symbiosys. Similar import enzymes have been found in all eukaryotic genomes sequenced to date. This lends credence to the notion that all eukaryotes are likely to be descendants of a single ancestor species that carried a ‘‘proto-mitochondrion,’’ an ancestral original mother, the “Eve” at the creation of modern cells.

The Mitochondrial Connection

It is now apparent that mitochondrial dysfunction plays a causal role in many disease states and that improvement in mitochondrial function could prove to be an important therapeutic goal. Indeed, studies have demonstrated that mitochondrial dysfunction is connected to obesity, insulin resistance, heart disease, and aging.

Endurance exercise (aka endurance training) is linked to enhanced mitochondria, increasing their size, number, and function, and consequently can help reduce the incidence of chronic disease. More robust mitochondria are associated with slowing down aging declines in function. Yet this type of exercise is time consuming, requiring many hours a week for the mitochondrial benefits.

Studies have demonstrated that mitochondrial dysfunction is connected to obesity, insulin resistance, heart disease, and aging.

It is also thought that improvements in metabolic and cardiovascular disease progression after treatment with pharmaceuticals—such as thiazolidinediones, or non-pharmaceutical treatments including caloric restriction—are at least partially mediated by increases in mitochondrial biogenesis and function. But drugs have their side-effects, and caloric restriction at the level required is daunting for all but the most dedicated.

The Genesis of Cellular Power

Mitochondrial biogenesis is the cellular process by which new mitochondria are formed. This process may be activated by a variety of different signals that occur during cellular stress or may result from environmental stimuli. The principal role of the mitochondrion is the regulation of cellular metabolic activity. Ironically, it is also a progenitor of free radicals, as well as a deactivator of their virulent activity. The more mitochondria you have—in number and in total mass—the better your cells are protected.

Mitochondrial biogenesis is regulated by a variety of pathways, which are possible therapeutic targets for slowing and even reversing endothelial dysfunction and concomitant vascular disease observed in metabolic diseases. In a growing number of studies, resveratrol has been shown to affect mitochondrial function in skeletal muscle and liver, but its role in mitochondrial biogenesis in endothelial cells has been relatively unexplored.

In a growing number of studies, resveratrol has been shown to affect mitochondrial function in skeletal muscle and liver, but its role in mitochondrial biogenesis in endothelial cells has been
relatively unexplored.

So it was with great interest that researchers, in a new study by Dr. Zoltan Ungvari and colleagues conducted at New York Medical College in Valhalla, NY, investigated whether resveratrol could induce mitochondrial biogenesis in human coronary arterial endothelial cells (CAECs).3 In CAECs, resveratrol increased mitochondrial mass and messenger DNA content, while up-regulating protein expression of electron transport chain constituents. Resveratrol also induced mitochondrial biogenesis factors including PGC-1α (see article
“Promoting Survival with Resveratrol” in the May 2008 issue and article
“The Antidiabetes Trigger” in the March 2009 issue).

The In Vivo Relevance of Mitochondrial Biogenesis

As well, resveratrol induced SIRT1, the now fabled sirtuin (sir·TOO·in) that has been the subject of front page headlines. SIRT1 is an enzyme that enables proteins that contribute to cellular regulation, including defense against stressors and enhanced longevity. Also, resveratrol up-regulated eNOS (endothelial nitric oxide synthase) in a SIRT1-dependent manner. When this form of NO synthesis is inhibited, resveratrol-induced mitochondrial biogenesis is dampened. NO is very important in this regard, along with many others uses (see article
“Can Nitric Oxide Increase Lifespan?” in the January 2006 issue).

In the Valhalla study, the aortas of type 2 diabetic mice with impaired mitochondrial biogenesis were normalized by resveratrol treatment, showing the in vivo relevance of the findings. The amount of resveratrol used was 20 mg/kg/d, which was begun when the mice were 10 weeks old and continued for 4 weeks. The human equivalent is 121.5 mg/d for a 75 kg human (about 165 lb). By activating SIRT1, resveratrol increased mitochondrial content in endothelial cells. The researchers proposed that SIRT1, via a pathway that involves up-regulation of eNOS, induces mitochondrial biogenesis. In any event, resveratrol induced mitochondrial biogenesis in the mice aortas, suggesting the potential for new treatment approaches targeting endothelial mitochondria in metabolic diseases.

While there have been many claims for the benefits of various supplements to help slow the aging process, in resveratrol we have a true prototype. Resveratrol is the first of its kind, a new class of supplements that mimics the effect of caloric restriction, hitherto the only way to increase maximum lifespan in a wide-range of animals.

But now, many of resveratrol’s researchers have set their goals as nothing less than the reversal of organ pathologies associated with aging and metabolic diseases. For undeniably, resveratrol has been shown to exert diverse anti-aging effects in lower animals. Yet while prior studies have concentrated on the effects of resveratrol on pro-inflammatory pathways and antioxidant defense mechanisms in endothelial cells, these have provided little information about its effects on endothelial mitochondria.

Dr. Ungvari and his researchers concluded that multiple mechanisms must be considered to explain resveratrol-induced mitochondrial biogenesis and its contribution to vascular health. Mitochondria impairment is also associated with reduced production of adenosine triphosphate (ATP), the principal transporter of intracellular energy. This in turn impairs the synthesis and secretion of endothelium-derived factors that generate important signals in the vascular wall.

Figure 1. Compared to untreated controls, resveratrol was shown to significantly increase the number of mitochondria in cultured CAECs. Relative mitochondrial mass was also increased significantly as was mitochondrial surface area. This last increase can be seen in the bar graph.

Was the increase in the number of mitochondria, their total mass, and surface area (see Fig. 1) in resveratrol-treated endothelial cells caused by the induction of mitochondrial biogenesis factors? By using advanced laboratory techniques, the expression of PGC-1α and other mitochondrial biogenesis factors were all found to increase, with the induction of PGC-1α viewed as the key modulator. In CAECs, resveratrol induced all the contributing factors to mitochondrial proliferation. And not to be dismissed, SIRT1 was also noted to play a critical role in resveratrol-induced effects in endothelial cells, thus extending what other studies have found from other cell types to endothelial cells.

Overexpression of SIRT1 also induces mitochondrial biogenesis in CAECs, mimicking the effects of resveratrol (based on unpublished observations). These findings are in accord with previous studies which showed that resveratrol and SIRT1 regulate mitochondrial function and mitochondrial biogenesis in skeletal muscle and liver tissues. It is likely that SIRT1 regulates multiple pathways involved in mitochondrial biogenesis in the endothelial cells, among which NO-dependent pathways appear to play a key role. In addition, SIRT1 may also directly deacetylate PGC-1α, thereby increasing its activity.

Dr. Ungvari et al. also demonstrated that inhibition of NO synthesis prevents resveratrol-induced mitochondrial biogenesis in CAECs. This suggests that NO may have a messenger signaling role in mediating the effects of resveratrol/SIRT1 in endothelial cells. Besides that, it was also found that a genetic lack of eNOS prevents resveratrol-induced mitochondrial biogenesis and upregulates mitochondrial biogenesis factors in cultured mouse arteries. Thus, it is significant that resveratrol was found in a SIRT1-dependent manner to upregulate eNOS both in cultured arteries and CAECs, providing a confirmation of results of previous studies.

When SIRT1 is overexpressed, eNOS is induced in cultured rat aortas and CAECs, and that, according to unpublished observations, may mimic the effect of resveratrol. While its precise role is unclear, NO plays a critical role in both the initiation and integration of the signaling events underlying mitochondrial biogenesis. Notably, when NO synthesis is inhibited significantly, there is a decrease in mitochondrial content. On the other side of the coin, NO donors increased mitochondrial mass in various cell types, including brown adipocytes and fat cells.

Keeping Mitochondria Abundant, Healthy, and Happy

As we age, there is an across-the-board loss of body function that is ultimately rooted in the deterioration that takes place at the level of our cells. Thus it is important to focus on enhancing the process whereby cellular components are continuous recycled, regenerated, and functionally maintained through our lives.

Fundamental among cellular components are mitochondria, which are especially valuable for healthy cells because of their role in energy production and management. Yet mitochondria are especially vulnerable to damage because their bioenergetic machinery renders them susceptible to intracellular oxidative stress.1

Mitochondrial biogenesis and turnover management (the clearance of defective mitochondria) are crucial for uninterrupted and dependable energy production. Equally important is the prevention of the damage that oxidative stress can cause as this too thwarts healthy aging. What is known is that there are a multitude of endogenous factors involved in the regulation of mitochondrial biogenesis many of which operate through PGC-1α (an abbreviation for PPAR gamma coactivator-1α; PPAR is the abbreviation for peroxisome proliferator-activated receptor). PGC-1α has a variety of activators including nitric oxide (made from arginine*), calorie restriction, and resveratrol, which mimics the effects of caloric restriction. Exercise has also been found to mimic caloric restriction by inducing mitochondrial biogenesis.

Other nutrients found valuable for mitochondrial health include:

D-alpha-tocopheryl succinate, the D-isomer form of vitamin E, because there are specific transporters for succinate in membranes around the mitochondria, where you especially want to deliver antioxidants because mitochondria are free radical hotbeds of activity.†

Coenzyme Q10 (in a cold-water-dispersible form), because CoQ10 plays an essential role in energy production in the mitochondria.‡

Melatonin, because it is a very powerful scavenger of hydroxyl radicals, highly reactive radicals that can react with and damage nearly every biomolecule, including nuclear DNA and mitochondrial DNA.§

Quercetin, because it has been shown to be an inhibitor of the mitochondrial membrane permeability transition (MMPT), the opening of an unselective pore elicited by calcium or prooxidants.|| Intramitochondrial quercetin appears to be functional for prevention of mitochondrial damage.2

Carnosine, and other antiglycating agents, because it has also been reported that the mitochondrial respiratory chain and the intracellular ATP content of cells are reduced by advanced glycation endproducts.#

Alpha lipoic acid, because studies have show that it can improve mitochondrial function in lab animals.3

Magnesium, because it is intimately involved in cellular energy metabolism in the mitochondria.**

Acetyl L-carnitine, because carnitine participates in energy production in most of our cells. It transports long-chain fatty acids to the interior of the cells’ mitochondria, where they are used as fuel for energy generation, and it transports some of the metabolic byproducts back out.††

Folic acid, vitamin B6, and vitamin B12, important vitamins that help prevent damage to mitochondria (where they help repair DNA damage), cofactor the production of nitric oxide, and reduce levels of homocysteine (a neurotoxin).‡‡

The generation of free radicals by mitochondria appears to be of much more importance in determining maximum lifespan than tissue antioxidant capacity. In other words, you get more protection from mechanisms that reduce the generation of free radicals in the first place, and especially in mitochondria, than you do from those that simply sop up the radicals after they have been generated.

For these reasons and others, it’s very important to maintain the vitality of your mitochondria by taking the appropriate supplements.

As previous studies suggest, the expression of mitochondrial biogenesis factors is probably regulated by the bioavailability of NO. (NO is generated by the amino acid arginine; see
“A New Treatment for Obesity” in the May issue.) As previously stated, diabetes and its complications have been correlated to reduced mitochondrial biogenesis. Combined with the knowledge that resveratrol probably exerts an additional benefit in preventing diabetes complications, the researchers were given extra motive to investigated its effect on vascular mitochondrial biogenesis in type 2 diabetes mellitus. In the type of mouse chosen for the study, type 2 diabetes is known to diminish mitochondrial biogenesis in the aorta.

Resveratrol significantly increased mitochondrial DNA content while inducing expression of mitochondrial biogenesis factors both in control and the diabetes-prone mice creating equivalency between the two groups. Thus, previous findings showing that resveratrol induces mitochondrial biogenesis in the liver and skeletal muscle were extended, attesting to the in vivo relevance of the researcher’s in vitro findings.

Type 2 diabetes mellitus is associated with both macrovascular and microvascular dysfunction, conditions characterized by reduced bioavailability of NO, which is believed to lead to the macrovascular complications of diabetes. In another recent study (Zhang and Ungvari, submitted), two of the same researchers demonstrated that resveratrol induces eNOS and significantly increases NO bioavailability in animal models of type 2 diabetes, even when mice were fed a high fat diet.

NO Bioavailability Restored by Resveratrol

NO is a key regulator of endothelial mitochondrial content. In accord, the Valhalla researchers attribute the mitochondrial biogenesis induced by resveratrol in diabetic mice to NO bioavailability restoration. This is consistent with a recent study showing that resveratrol can recapitulate many of caloric restriction’s molecular downstream events.4 Caloric restriction also induces eNOS and promotes mitochondrial biogenesis, it has been found. Another factor that may contribute to resveratrol’s vasoprotective effects is the finding that it might improve endocrine regulation of cellular metabolism. Other clinical trials currently underway are confirming that the use of resveratrol in humans is safe and does not result in any significant side-effects.

This is consistent with a recent study showing that resveratrol can recapitulate many of
caloric restriction’s molecular downstream events.

What’s True for Mice . . .

To recap, at physiologically relevant concentrations, resveratrol increases mitochondrial content in endothelial cells through the activation of SIRT1. This in turn—using a pathway that upregulates eNOS—induces mitochondrial biogenesis factors (including PGC1α), thereby promoting mitochondrial biogenesis. In type 2 diabetic mice, resveratrol was found to induce mitochondrial biogenesis in their aortas. That’s good news. What’s true for mice is likely to be true for us. Supplements that mimic caloric restriction—and resveratrol remains the champ—have great potential to improve endothelial mitochondria and to help ward off metabolic diseases.